Drafting machine



May 28, 1963 w. PIEPER 3,091,036

DRAFTING MACHINE Filed sept. 22, 1959 United States Patent O 3,091,036 DRAFTING MACHINE Willi Pieper, Seestrasse 71, Kilchberg, Zurich, Switzerland Filed Sept. 22, 1959, Ser. No. 841,540 Claims. (Cl. 33-79) The present invention relates to a drafting machine provided with rollers, located at the pivot points of the drafting machine linkage, which are connected to each other in pairs by flexible draw tapes.

Drafting machines not operated in the approximately horizontal position have the tendency of slipping down on the drawing board due to the eect of the vertical component of weight `of the head and part of the linkage. To eliminate these undesirable vertical components of weight, counterweights or spring-loaded retarding devices are used. However, the use of counterweights has the great disadvantages that the weight of the machine is considerably increased-nearly doubled-and that in the positions of the drafting machine approaching the horizontal there is a tendency for the linkage and the drawing squares to tbe lifted off the drawing board. Spring-loaded retarding devices are also not able to solve the problem faultlessly for the reason that such retarding devices are capable of producing their optimum action only in one definite inclined position of the drafting machine whereas in all other inclined positions they are not able to balance exactly the weight of the head. Readjustment of the spring action to t the positions of the board, while helpful, is rather cumbersome.

According to the present invention, the existing problem is to be solved by fitting a brake device between two parts of the drafting machine linkage angular-ly offset from each other on the movable linkage, said brake device being operative in `one direction only in such a manner that in all positions of the drawing machine other than the horizontal the brake counteracts the vertical component of weight of the drafting machine head and its linkage but is inoperative upon the upward displacement of the drafting machine head.

By way of example, an embodiment of the invention is illustrated in the accompanying drawing in which:

FIG. l is an axial section through the top member of a drafting machine utilizing transmission tapes;

FIG. 2 is a detailed view of a part of FIG. l drawn to an enlarged scale;

FIG. 3 a cross-sectional view taken on the line III- Ill of FIG. 2; and

FIG. 4 a further cross-sectional view taken on the line IVIV of FIG. 2.

ln the drawing the numeral A1 indicates the top roller of the tape drafting machine, said roller being rigidly connected to an anchorage block or base (not shown) secured to the drawing board. The numeral 2 indicates the casing surrounding the tape roller 1, the tubes 3 and 4 of the top member of the drafting machine linkage being screwed into said casing. The numeral 5 designates a steel tape enclosed in the tube 3, said steel tape 5 being connected to the stationary roller 1 in known friction-proof or true-to-shape manner.

Between the tube 3 and the tape 5 there is provided a brake -device in the interior of the tube 3. Said brake device comprises a cylindrical brake body 6 of a crosssection corresponding to the inside diameter of the tube 3. 'I'he tape 5 passes through a longitudinal slot 6a in brake body 6. A wedge 7 is displaceably mounted on an inclined surface 6b of the longitudinal slot 6a and the brake body respectively. For easy displaceability of the wedge 7 there is provided an anti-friction bearing between it and the inclined surface 6b. This anti-friction bearing is formed by the 1balls 8 guided in longitudinal grooves 7a, 6c of the Wedge 7 and the brake body 6 re- Patented May 28, l 963 spectively. Both the brake body and the wedge 7 are provided with brake linings 9 and 10 respectively on their surfaces confronting the tape 5. The numeral 11 designates a leaf spring anchored at one end in the brake body 6, the other end of the spring resting against the face of the wedge 7 and urging the latter into engagement with the inclined surface 6b of the brake body 6 and into constant contact with the tape 5. A11 adjusting means is provided for limiting the engaging motion of the wedge 7. This means consists of a threaded nut 12 engaging an external screw thread 3a provided on the tube 3, said nut 12 being provided ywith an annular groove 13 in its inner surface which engages a pin 14 extending transversely across the path of the wedge 7. The pin 14 passes through longitudinal slot 15 provided in the tube 3. The numeral 16 designates an abutment pin secured to the wedge 7, said pin 16 serving as a stop for the Wedge 7 and preventing the wedge 7 from dropping out of the lbrake body 6 or from protruding too far out of it.

As is particularly apparent from FIG. 2, the inclined surface 6b of the brake body 6 is -biased in such a way that the brake device cornes into operation upon the tape 5 being drawn in the direction of the arrow A shown in FIG. 2 whilst the brake is released when the tape is drawn in the direction of arrow B.

By a cage (not shown) the balls 8 of the anti-friction bearing are kept spaced and prevented from dropping out of their guides.

The mode of operation of the brake device described Vabove is as follows:

In inclined or vertical positions of the drafting machine, under the force of the vertical component of the weight of the drafting machine and its linkage, the top linkage member 2, 3, 4 has a tendency to pivot about the axis 1a of the roller 1 in the direction of arrow C in FIG. l. When such a pivoting motion occurs, the tape 5 is wound onto the roller 1, the tape 5 being displaced relatively to the tube 3 in the `direction of arrow A. Now the tape 5 moving in the tube 3` in the direction shown by arrow A tends to carry along the wedge 7 with the result that the wedge 7 runs on to the inclined camming surface 6b of the brake body 6 so as to engage the tape with a cor-responding pressure and to produce a brake action. It is this brake action which prevents the drafting machine from sliding downwardly on the inclined or vertical drawing board. To prevent the occurrence of a self-locking action between the wedge 7 and the tape 5, the displacement of the wedge 7 in the direction of braking is limited by the adjusting means 12, 14. Upon a turning of the threaded nut 12 in .one sense the pin -14 engaging the annular groove 13 presses against the wedge 7 so that the latter cannot run on to the inclined surface 6b of the brake body beyond a certain desired extent. In this manner the brake action corresponding to the necessary balance of weight of the drafting machine can be accurately adjusted.

lf the drafting machine head is pushed upwardly, the top linkage member illustrated in FIG. l is pivoted about the axis 1a in the direction opposite to arrow C, the tape 5 being displaced relatively to the tube 3 in the direction of arr-ow B. Owing to the frictional contact existing between the wedge '7 and the tape 5, the wedge is now slightly displaced in the direction of arrow B and thereby released so that upon pushing the drafting machine head upwardly the brake device is inactivated. Thus with an upward movement of the drafting machine head it is no longer necessary to overcome a braking force designed to equalize the vertical component of weight.

It is also possible to make the inclination of the inclined surface 6b of the brake body 6 relative to the tape 5 such that no self-locking action at all can occur.

What I claim is:

l. In a drafting machine, in combination, a parallelmotion linkage including a pivotal roller, an arm swingable about said roller, said arm being formed with two parallel passages extending tangentially from said roller, and an elongated transmission element in said passages connecting said roller with a remote head `for angular displacement of the latter with respect to said anm upona rotation of said arm about said roller; and unidirectionally effective brake means disposed in `one of said passages and adapted to engage said element for at least limitedly retail-ding the rotation of said arm about said roller in one sense and permitting relatively unretarded rotation in the opposite sense, said brake means including Wedge means frictionally engaging said element upon said rotation of said arm in said one sense.

2. In a drafting machine, in combination, a parallelmotion linkage including a pivotal roller, an arm swingable about said roller, and an elongated transmission element connecting said roller with a remote head for angular displacement of the latter with respect to said arm upon a rotation of said arm about said roller, unidirectionally effective brake means on said arm adapted to engage said element for at least limitedly retarding the rotation of said arm about said roller in one sense and permitting relatively unretarded rotation in the opposite sense; and adjustment means -for regulating the degree of engagement of said brake means with said element.

3. In a drafting machine, in combination, a parallelmotion linkage including a pivotal roller, an arm swingable about said roller, said arm being formed with two parallel passages extending tangentially from said roller, and an elongated transmission element in said passages connecting said roller with said remote head -for angular Adisplacement of the latter with yrespect to said arm upon a rotation of said arm about said roller; unidirectionally eiectivebrake means disposed in one of said passages adapted to engage said element for at least limitedly retarding the rotation of said arm about said roller in one sense and permitting relatively unretarded rotation in the opposite sense, said brake means including a wedge longitudinally displaceable in said one passage into frictional engagement with said element upon the rotation of said arm in said one sense; and adjustment means for regulating the displacement of said Wedge, thereby controlling the degree of engagement of said wedges with said element.

4. In a drafting machine, in combination, a parallel- Y motion linkage including a pivotal roller, an arm swingable about said roller, saidiar-m being formed with two parallel passages extending -tangentially from said roller, and an elongated transmission element in said passages connecting said roller With-said remote head for angular displacement of the latter -With respect to said arm upon a rotation `of said arm about said roller; and unidirectional Ibrake means disposed in one of said passages adapted to engage said element for at least limitedly retarding the rotation of said a-rm about said roller in one sense and permitting relatively unretarded rotation in the opposite sense, said brake means comprising a body partially lling said one passage and surrounding said `element with clearance, a wedge member longitudinally shiftable into the clearance between said body and said element for `frictionally engaging said element between said body and said Wedge member, and biasing means urging said wedge member into said clearance.

5. in a drafting machine, in combination, atparallelmotion linkage including a pivotal roller, an arm swingable about said roller, said arm =being formed with two parallel passages extending tangentially from said roller, and an elongated transmission element in said passages connecting said roller with said remote head for angular displacement of the latter vwit-h respect to said arm upon a rotation of said arm about said roller; unidirectional brake means disposed in one of said passages adapted to engage said element for at least limitedly retarding the rotation of said arm about said roller in one sense and :permitting relatively unretarded rotation in the opposite sense, said brake means comprising a body partially filling said one passage and surrounding said element with clearance, a wedge member .longitudinally shi-ftable into the clearance between said body and said element for frictionally engagingy said element between said body and said wedge mem-bemand biasing means urging said wedge member into said clearance; and adjustment means for regulating the displacement of said wedge member, there-Y by controlling the degree of engagement of said wedge member with said element.

r4'References Cited in the le of this patent UNITED STATES PATENTS 2,217,008 Garner Oct. 8, 1940 2,552,335 Little May 8, 19511 2,808,129 Kraus Oct. 1, 1957 2,939,550 Puttre June 7, 1960 

1. IN A DRAFTING MACHINE, IN COMBINATION, A PARALLELMOTION LINKAGE INCLUDING A PIVOTAL ROLLER, AN ARM SWINGABLE ABOUT SAID ROLLER, SAID ARM BEING FORMED WITH TWO PARALLEL PASSAGES EXTENDING TANGENTIALLY FROM SAID ROLLER, AND AN ELONGATED TRANSMISSION ELEMENT IN SAID PASSAGES CONNECTING SAID ROLLER WITH A REMOTE HEAD FOR ANGULAR DISPLACEMENT OF THE LATTER WITH RESPECT TO SAID ARM UPON A ROTATION OF SAID ARM ABOUT SAID ROLLER; AND UNIDIRECTIONAL LY EFFECTIVE BRAKE MEANS DISPOSED IN ONE OF SAID PASSAGES AND ADAPTED TO ENGAGE SAID ELEMENT FOR AT LEAST LIMITEDLY RETARDING THE ROTATION OF SAID ARM ABOUT SAID ROLLER IN ONE SENSE AND PERMITTING RELATIVELY UNRETARDED ROTATION IN THE OPPOSITE SENSE, SAID BRAKE MEANS INCLUDING WEDGE MEANS FRICTIONALLY ENGAGING SAID ELEMENT UPON SAID ROTATION OF SAID ARM IN SAID ONE SENSE. 